If the Secretary of State’s speculations about religion come off as grandiose, naive or false, it’s because they indeed are. To anyone who has ever studied the bedrock text of the three Abrahamic religions, the Old Testament, Kerry’s proclamation is a theological head-scratcher.

Did Mr. Kerry miss that part in Deuteronomy where the Bible says in no uncertain terms, concerning a city where the majority of Israelites had started to worship a deity aside from the Judaic one, to “smite the inhabitants of that city with the edge of the sword, destroying it utterly, and all that is therein and the cattle thereof, with the edge of the sword” (13,16)?

Or when Deuteronomy outlines the genocidal commandment to "blot out the memory of Amalek from under the heaven” (25,19)?

The Jewish Talmud and early legal authorities codify these verses, affirming that the religious obligation to decimate an entire town includes killing all its men, women and children, regardless of whether or not they themselves had worshipped the foreign deity, and that blotting out the nation of Amalek also entails putting to death all its men, women and children.

If that sounds like extremism, terrorism, or the corruption of a peaceful religion’s words for political purposes, it isn’t. It’s actually a very straightforward reading of the texts, and is considered normative Orthodox Jewish law.

It may come as a shock to Secretary Kerry or modern Jews, but the Old Testament is violent and punitive. It isn’t a pluralistic document. Many of its precepts do not fit modern notions of liberal democracy and self-determination.

But if this foray into Biblical study comes off as irrelevant, that’s because the astute observer can concede that it largely is. Jews probably never fulfilled these commandments when they lived in Biblical Israel, and certainly don’t use it as pretext to commit acts of terrorism nowadays.

In a riveting essay for The Atlantic published the week before Kerry’s op-ed, Graeme Wood interviewed Princeton scholar Bernard Haykel, a leading expert on the Islamic State’s ideology. Haykel astutely observes that Islam isn’t merely a static reading of religious text: “It’s what Muslims do, and how they interpret their texts.”

What is true about Judaism is true of Christianity, Buddhism, and yes, Islam: religion is not monolithic. Its interpretations and practices are shaped by historical, political and cultural pressures. Today’s Jews recoil in horror from the thought of killing children, even though the Bible commands it, and most Muslims today oppose the religiously-sanctioned terrorism employed by ISIS, Al-Qaeda and the Taliban.

Kerry’s desire to not alienate moderate Muslims and show that the West is not at war with Islam is commendable. We indeed are not at war with Islam and its majority of moderate Muslims. His rhetoric, however, is incredibly naive, and may actually do more harm than good in the fight against Islamist extremism.

So too, when President Obama proclaimed (employing the term ISIL to refer to Islamic State) that “ISIL is not Islamic,” he avoided a key opportunity to combat ISIS’s radical ideology.

ISIS is indeed Islamic. As Wood explains at length, it’s an organization hell-bent on bringing about the apocalypse, destroying the West and ushering in the coming of the Mahdi, a prominent messiah figure in Islam. These goals are not merely religiously-masked political objectives: they are scholarly, Salafist interpretations of the Qu’ran and the Hadiths which draw on seventh century Islamic practice. They are religious, Islamic goals. Full stop.

Kerry and Obama’s points about the group’s political aims are prudent: it is impossible to understand the rise of ISIS, the Muslim Brotherhood or other Islamist groups without taking into account political and economic factors, such as the decline of the Ottoman Empire after World War I; the West’s disastrous carving up of the Middle East after Sykes-Picot; and the oppressive, socially backwards and economically stagnant societies that secularist Arab regimes have created.

Islamism isn’t a purely religious answer to the Middle East’s dilemmas. It is a political expression of Islam that has found favor among some Muslims today seeking a better life.

Disenfranchised Muslims in failing Arab states will indeed be more easily drawn to the extremism of ISIS. A New York Times profile of Islam Yaken, a young Egyptian man turned ISIS foot-soldier, shows how a failing Egyptian economy and political alienation following Abdel Fattah el-Sisi’s coup d'etat creates fertile ground for jihadist recruiting.

But to combat its potentially dangerous consequences, the West must understood the Islamist ideology. To deny its religious nature and roots is to battle it blind, and leave frustrated young Muslims in failing Arab countries vulnerable to its attractive promises: Democracy hasn’t brought us success, so why not return to Islamism and the heyday of Muslim power and glory?

By rebutting the religious arguments of Islamism and advocating more moderate forms of Islam, the West can help discourage possible recruits from joining ISIS, which can tangibly degrade the group’s military capabilities, and help push Arab countries towards more stable forms of democracy.

There is also a public relations issue in not calling the Islamist spade a spade. Much of the Arab world acknowledges that Islamic radicalism is a cancer destroying Muslim communities from the inside out: Egyptian president el-Sisi’s recent speech at Cairo University, a prominent center for Islamic study and thought, has called for a “religious revolution...because the Islamic world is being torn, it is being destroyed, it is being lost. And it is being lost by our own hands.”

The key to stabilizing the Middle East lies with such moderate regimes as el-Sisi’s. If the leader of the free world and his administration cannot agree with Arab leaders regarding the ideological nature of the threats facing these regimes, it only undermines those leaders’ efforts to persuade an agitated citizenry which still needs to be convinced of the merits of more secular governance.

Religion can be brutal. ISIS is Islamic. Messrs Kerry and Obama ought to acknowledge that.